Battle of Pelennor Fields (3019 T.A.) - Sauron's all-out attempt to conquer Gondor, the most powerful kingdom of Men in Middle Earth.

"New forces of the enemy were hastening up the road from the River; and from under the walls came the legions of Morgul; and from the southward fields came footman of Harad with horsemen before them, and behind them rose the huge backs of the mûmakil with war-towers upon them.  But northward the white crest of Éomer led the great front of the Rohirrim which he had again gathered and marshaled, and out of the City came all the strength of men that was in it, and the silver swan of Dol Amroth was borne in the van, driving the enemy from the Gate." ~The Return of the King, Book V, chap. 6 (The Battle of the Pelennor Fields)